Conventionally, “PET-CT apparatuses” in each of which a Positron Emission Tomography apparatus (hereinafter, a “PET apparatus”) and an X-ray Computed Tomography (CT) apparatus are combined together have been in practical use. Further, in recent years, “PET-MRI apparatuses” in each of which a PET apparatus and a Magnetic Resonance Imaging apparatus (hereinafter, an “MRI apparatus”) are combined together are also expected to be in practical use. For example, PET-MRI apparatuses are expected to be in practical use for an early diagnosis of Alzheimer's disease.